Essentials of Human Anatomy & Physiology, Chapter 15 Urinary System - 12th Edition PDF

Chapter 15 The Urinary System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College © 2018 Pearson Education, Inc.  Fu...

Chapter 15 The Urinary System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College © 2018 Pearson Education, Inc.  Functions of the Urinary System  Kidneys dispose of waste products in urine  Nitrogenous wastes  Toxins  Drugs  Excess ions  Kidneys’ regulatory functions include:  Production of renin to maintain blood pressure  Production of erythropoietin to stimulate red blood cell production  Conversion of vitamin D to its active form © 2018 Pearson Education, Inc.  Organs of the Urinary System  Kidneys  Ureters  Urinary bladder  Urethra © 2018 Pearson Education, Inc. Figure 15.1a Organs of the urinary system. Hepatic veins (cut) Inferior vena cava Adrenal gland Renal artery Renal hilum Aorta Renal vein Kidney Iliac crest Ureter Rectum (cut) Uterus (part of female Urinary reproductive bladder system) Urethra (a) © 2018 Pearson Education, Inc.  Kidneys  Location and structure  The kidneys are situated against the dorsal body wall in a retroperitoneal position (behind the parietal peritoneum)  The kidneys are situated at the level of the T12 to L3 vertebrae  The right kidney is slightly lower than the left (because of position of the liver) © 2018 Pearson Education, Inc. Figure 15.1b Organs of the urinary system. 12th rib (b) © 2018 Pearson Education, Inc.  Kidneys  Kidney structure  An adult kidney is about 12 cm (5 in) long and 6 cm (2.5 in) wide  Renal hilum  A medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves)  An adrenal gland sits atop each kidney © 2018 Pearson Education, Inc.  Kidneys  Kidney structure (continued)  Three protective layers enclose the kidney  Fibrous capsule encloses each kidney  Perirenal fat capsule surrounds the kidney and cushions against blows  Renal fascia is the most superficial layer that anchors the kidney and adrenal gland to surrounding structures © 2018 Pearson Education, Inc.  Kidneys  Kidney structure (continued)  Three regions revealed in a longitudinal section 1. Renal cortex—outer region 2. Renal medulla—deeper region  Renal (medullary) pyramids—triangular regions of tissue in the medulla  Renal columns—extensions of cortexlike material that separate the pyramids © 2018 Pearson Education, Inc.  Kidneys  Kidney structure (continued)  Three regions (continued) 3. Renal pelvis—medial region that is a flat, funnel- shaped tube  Calyces form cup-shaped ―drains‖ that enclose the renal pyramids  Calyces collect urine and send it to the renal pelvis, on to the ureter, and to the urinary bladder for storage © 2018 Pearson Education, Inc. Figure 15.2a Internal anatomy of the kidney. Renal cortex Renal column Major calyx Minor calyx Renal pyramid (a) © 2018 Pearson Education, Inc. Figure 15.2b Internal anatomy of the kidney. Cortical radiate vein Cortical radiate artery Renal cortex Arcuate vein Arcuate artery Renal column Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Minor calyx Renal pelvis Major calyx Renal Ureter pyramid Fibrous capsule (b) © 2018 Pearson Education, Inc.  Kidneys  Blood supply  One-quarter of the total blood supply of the body passes through the kidneys each minute  Renal artery provides each kidney with arterial blood supply  Renal artery divides into segmental arteries → interlobar arteries → arcuate arteries → cortical radiate arteries © 2018 Pearson Education, Inc.  Kidneys  Venous blood flow  Cortical radiate veins → arcuate veins → interlobar veins → renal vein  There are no segmental veins  Renal vein returns blood to the inferior vena cava © 2018 Pearson Education, Inc. Figure 15.2b Internal anatomy of the kidney. Cortical radiate vein Cortical radiate artery Renal cortex Arcuate vein Arcuate artery Renal column Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Minor calyx Renal pelvis Major calyx Renal Ureter pyramid Fibrous capsule (b) © 2018 Pearson Education, Inc. Figure 15.2c Internal anatomy of the kidney. Aorta Renal Segmental Interlobar Arcuate Cortical Afferent artery artery artery artery radiate arteriole artery Glomerulus (capillaries) Inferior Renal Interlobar Arcuate Cortical Peritubular Efferent vena vein vein vein radiate capillaries arteriole cava vein (c) © 2018 Pearson Education, Inc.  Nephrons  Structural and functional units of the kidneys  Each kidney contains over a million nephrons  Each nephron consists of two main structures 1. Renal corpuscle 2. Renal tubule © 2018 Pearson Education, Inc. Figure 15.3a Structure of the nephron. Cortical nephron Fibrous capsule Renal cortex Collecting duct Renal medulla Renal Proximal Renal pelvis cortex convoluted tubule Glomerulus Ureter Juxtamedullary Distal convoluted tubule nephron Nephron loop Renal medulla (a) © 2018 Pearson Education, Inc.  Nephrons  Renal corpuscle consists of: 1. Glomerulus, a knot of capillaries made of podocytes  Podocytes make up the inner (visceral) layer of the glomerular capsule  Foot processes cling to the glomerulus  Filtration slits create a porous membrane—ideal for filtration 2. Glomerular (Bowman’s) capsule is a cup-shaped structure that surrounds the glomerulus  First part of the renal tubule © 2018 Pearson Education, Inc. Figure 15.3c Structure of the nephron. Glomerular PCT capsular space Glomerular capillary covered by podocytes Efferent arteriole Afferent arteriole (c) © 2018 Pearson Education, Inc. Figure 15.3d Structure of the nephron. Filtration slits Podocyte cell body Foot processes (d) © 2018 Pearson Education, Inc.  Nephrons  Renal tubule  Extends from glomerular capsule and ends when it empties into the collecting duct  From the glomerular (Bowman’s) capsule, the subdivisions of the renal tubule are: 1. Proximal convoluted tubule (PCT) 2. Nephron loop (loop of Henle) 3. Distal convoluted tubule (DCT) © 2018 Pearson Education, Inc. Figure 15.3a Structure of the nephron. Cortical nephron Fibrous capsule Renal cortex Collecting duct Renal medulla Renal Proximal Renal pelvis cortex convoluted tubule Glomerulus Ureter Juxtamedullary Distal convoluted tubule nephron Nephron loop Renal medulla (a) © 2018 Pearson Education, Inc. Figure 15.3b Structure of the nephron. Proximal convoluted Peritubular tubule (PCT) Glomerular capillaries capillaries Distal convoluted tubule Glomerular (DCT) (Bowman’s) capsule Efferent arteriole Afferent arteriole Cells of the juxtaglomerular apparatus Cortical radiate artery Arcuate artery Arcuate vein Cortical radiate vein Collecting duct Nephron loop (b) © 2018 Pearson Education, Inc.  Nephrons  Cortical nephrons  Located entirely in the cortex  Include most nephrons  Juxtamedullary nephrons  Found at the cortex-medulla junction  Nephron loop dips deep into the medulla  Collecting ducts collect urine from both types of nephrons, through the renal pyramids, to the calyces, and then to the renal pelvis © 2018 Pearson Education, Inc. Figure 15.3a Structure of the nephron. Cortical nephron Fibrous capsule Renal cortex Collecting duct Renal medulla Renal Proximal Renal pelvis cortex convoluted tubule Glomerulus Ureter Juxtamedullary Distal convoluted tubule nephron Nephron loop Renal medulla (a) © 2018 Pearson Education, Inc.  Nephrons  Two capillary beds associated with each nephron 1. Glomerulus 2. Peritubular capillary bed © 2018 Pearson Education, Inc.  Nephrons  Glomerulus  Fed and drained by arterioles  Afferent arteriole—arises from a cortical radiate artery and feeds the glomerulus  Efferent arteriole—receives blood that has passed through the glomerulus  Specialized for filtration  High pressure forces fluid and solutes out of blood and into the glomerular capsule © 2018 Pearson Education, Inc. Figure 15.3c Structure of the nephron. Glomerular PCT capsular space Glomerular capillary covered by podocytes Efferent arteriole Afferent arteriole (c) © 2018 Pearson Education, Inc.  Nephrons  Peritubular capillary beds  Arise from the efferent arteriole of the glomerulus  Low-pressure, porous capillaries  Adapted for absorption instead of filtration  Cling close to the renal tubule to receive solutes and water from tubule cells  Drain into the interlobar veins © 2018 Pearson Education, Inc. Figure 15.3b Structure of the nephron. Proximal convoluted Peritubular tubule (PCT) Glomerular capillaries capillaries Distal convoluted tubule Glomerular (DCT) (Bowman’s) capsule Efferent arteriole Afferent arteriole Cells of the juxtaglomerular apparatus Cortical radiate artery Arcuate artery Arcuate vein Cortical radiate vein Collecting duct Nephron loop (b) © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Urine formation is the result of three processes 1. Glomerular filtration 2. Tubular reabsorption 3. Tubular secretion © 2018 Pearson Education, Inc. Figure 15.4 The kidney depicted schematically as a single large, uncoiled nephron. Afferent arteriole Glomerular capillaries Efferent Cortical arteriole radiate artery Glomerular 1 capsule Three major renal processes: Rest of renal tubule 1 1 Glomerular filtration: Water and solutes containing smaller than proteins are forced through the filtrate capillary walls and pores of the glomerular capsule into the renal tubule. Peritubular 2 capillary 2 Tubular reabsorption: Water, glucose, amino acids, and needed ions are 3 transported out of the filtrate into the tubule cells and then enter the capillary blood. To cortical radiate vein 3 Tubular secretion: H1, K1, creatinine, and drugs are removed from the peritubular blood and secreted by the tubule cells into the Urine filtrate. © 2018 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Urine Formation and Characteristics  Glomerular filtration  The glomerulus is a filter  Filtration is a nonselective passive process  Water and solutes smaller than proteins are forced through glomerular capillary walls  Proteins and blood cells are normally too large to pass through the filtration membrane  Once in the capsule, fluid is called filtrate  Filtrate leaves via the renal tubule © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Glomerular filtration (continued)  Filtrate will be formed as long as systemic blood pressure is normal  If arterial blood pressure is too low, filtrate formation stops because glomerular pressure will be too low to form filtrate © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Tubular reabsorption  The peritubular capillaries reabsorb useful substances from the renal tubule cells, such as:  Water  Glucose  Amino acids  Ions  Some reabsorption is passive; most is active (ATP)  Most reabsorption occurs in the proximal convoluted tubule © 2018 Pearson Education, Inc. Figure 15.5 Sites of filtration, reabsorption, and secretion in a nephron. Proximal tubule Distal tubule Glomerular HCO3− Glucose and capsule NaCl NaCl H2O amino acids Blood Some drugs H+ K+ and and poisons some Collecting Filtrate duct drugs H2O Cortex Salts (NaCl, etc.) Medulla HCO3− (bicarbonate) H+ H2O Urea Nephron loop NaCl Glucose; amino acids Some drugs NaCl H2O Reabsorption K+ Active transport Passive transport Urea Secretion NaCl H2O (active transport) Urine (to renal pelvis) © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Tubular secretion  Reabsorption in reverse  Some materials move from the blood of the peritubular capillaries into the renal tubules to be eliminated in filtrate  Hydrogen and potassium ions  Creatinine © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Tubular secretion (continued)  Secretion is important for:  Getting rid of substances not already in the filtrate  Removing drugs and excess ions  Maintaining acid-base balance of blood  Materials left in the renal tubule move toward the ureter © 2018 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Urine Formation and Characteristics  Nitrogenous wastes  Nitrogenous waste products are poorly reabsorbed, if at all  Tend to remain in the filtrate and are excreted from the body in the urine  Urea—end product of protein breakdown  Uric acid—results from nucleic acid metabolism  Creatinine—associated with creatine metabolism in muscles © 2018 Pearson Education, Inc. Figure 15.5 Sites of filtration, reabsorption, and secretion in a nephron. Proximal tubule Distal tubule Glomerular HCO3− Glucose and capsule NaCl NaCl H2O amino acids Blood Some drugs H+ K+ and and poisons some Collecting Filtrate duct drugs H2O Cortex Salts (NaCl, etc.) Medulla HCO3− (bicarbonate) H+ H2O Urea Nephron loop NaCl Glucose; amino acids Some drugs NaCl H2O Reabsorption K+ Active transport Passive transport Urea Secretion NaCl H2O (active transport) Urine (to renal pelvis) © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  In 24 hours, about 1.0 to 1.8 liters of urine are produced  Urine and filtrate are different  Filtrate contains everything that blood plasma does (except proteins)  Urine is what remains after the filtrate has lost most of its water, nutrients, and necessary ions through reabsorption  Urine contains nitrogenous wastes and substances that are not needed © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Urine characteristics  Clear and pale to deep yellow in color  Yellow color is normal and due to the pigment urochrome (from the destruction of hemoglobin) and solutes  Dilute urine is a pale, straw color  Sterile at the time of formation  Slightly aromatic, but smells like ammonia with time  Slightly acidic (pH of 6)  Specific gravity of 1.001 to 1.035 © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Solutes normally found in urine  Sodium and potassium ions  Urea, uric acid, creatinine  Ammonia  Bicarbonate ions © 2018 Pearson Education, Inc.  Urine Formation and Characteristics  Solutes NOT normally found in urine  Glucose  Blood proteins  Red blood cells  Hemoglobin  WBCs (pus)  Bile © 2018 Pearson Education, Inc. Table 15.1 Abnormal Urinary Constituents © 2018 Pearson Education, Inc.  Ureters  Slender tubes 25–30 cm (10–12 inches) attaching the kidney to the urinary bladder  Continuous with the renal pelvis  Enter the posterior aspect of the urinary bladder  Run behind the peritoneum  Peristalsis aids gravity in urine transport © 2018 Pearson Education, Inc. Figure 15.1a Organs of the urinary system. Hepatic veins (cut) Inferior vena cava Adrenal gland Renal artery Renal hilum Aorta Renal vein Kidney Iliac crest Ureter Rectum (cut) Uterus (part of female Urinary reproductive bladder system) Urethra (a) © 2018 Pearson Education, Inc. Figure 15.6 Basic structure of the female urinary bladder and urethra. Urinary bladder Ureter Ureteral orifice Internal urethral Trigone orifice External urethral Internal urethral sphincter sphincter Urogenital diaphragm Urethra © 2018 Pearson Education, Inc.  Urinary Bladder  Smooth, collapsible, muscular sac situated posterior to the pubic symphysis  Stores urine temporarily  Trigone—triangular region of the urinary bladder base based on three openings  Two openings from the ureters (ureteral orifices)  One opening to the urethra (internal urethral orifice)  In males, the prostate surrounds the neck of the urinary bladder © 2018 Pearson Education, Inc. Figure 15.6 Basic structure of the female urinary bladder and urethra. Urinary bladder Ureter Ureteral orifice Internal urethral Trigone orifice External urethral Internal urethral sphincter sphincter Urogenital diaphragm Urethra © 2018 Pearson Education, Inc.  Urinary Bladder  Wall of the urinary bladder  Three layers of smooth muscle collectively called the detrusor muscle  Mucosa made of transitional epithelium  Walls are thick and folded in an empty urinary bladder  Urinary bladder can expand significantly without increasing internal pressure © 2018 Pearson Education, Inc.  Urinary Bladder  Capacity of the urinary bladder  A moderately full bladder is about 5 inches long and holds about 500 ml of urine  Capable of holding twice that amount of urine © 2018 Pearson Education, Inc. Figure 15.7 Position and shape of a distended and an empty urinary bladder in an adult male. Umbilicus Superior wall of distended bladder Superior wall of empty bladder Pubic symphysis © 2018 Pearson Education, Inc.  Urethra  Thin-walled tube that carries urine from the urinary bladder to the outside of the body by peristalsis  Function  Females—carries only urine  Males—carries urine and sperm © 2018 Pearson Education, Inc.  Urethra  Release of urine is controlled by two sphincters 1. Internal urethral sphincter  Involuntary and made of smooth muscle 2. External urethral sphincter  Voluntary and made of skeletal muscle © 2018 Pearson Education, Inc. Figure 15.6 Basic structure of the female urinary bladder and urethra. Urinary bladder Ureter Ureteral orifice Internal urethral Trigone orifice External urethral Internal urethral sphincter sphincter Urogenital diaphragm Urethra © 2018 Pearson Education, Inc.  Urethra  Length  In females: 3 to 4 cm (1.5 inches long)  In males: 20 cm (8 inches long)  Location  Females—anterior to the vaginal opening  Males—travels through the prostate and penis  Prostatic urethra  Membranous urethra  Spongy urethra © 2018 Pearson Education, Inc. Figure 15.6 Basic structure of the female urinary bladder and urethra. Urinary bladder Ureter Ureteral orifice Internal urethral Trigone orifice External urethral Internal urethral sphincter sphincter Urogenital diaphragm Urethra © 2018 Pearson Education, Inc.  Micturition  Micturition  Voiding, or emptying of the urinary bladder  Two sphincters control the release of urine, the internal urethral sphincter and external urethral sphincter  Bladder collects urine to 200 ml  Stretch receptors transmit impulses to the sacral region of the spinal cord  Impulses travel back to the bladder via the pelvic splanchnic nerves to cause bladder contractions © 2018 Pearson Education, Inc.  Micturition  When contractions become stronger, urine is forced past the involuntary internal sphincter into the upper urethra  Urge to void is felt  The external sphincter is voluntarily controlled, so micturition can usually be delayed © 2018 Pearson Education, Inc.  Fluid, Electrolyte, and Acid-Base Balance  Blood composition depends on three factors 1. Diet 2. Cellular metabolism 3. Urine output © 2018 Pearson Education, Inc.  Fluid, Electrolyte, and Acid-Base Balance  Kidneys have four roles in maintaining blood composition 1. Excreting nitrogen-containing wastes (previously discussed) 2. Maintaining water balance of the blood 3. Maintaining electrolyte balance of the blood 4. Ensuring proper blood pH © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Normal amount of water in the human body  Young adult females = 50%  Young adult males = 60%  Babies = 75%  The elderly = 45%  Water is necessary for many body functions, and levels must be maintained © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Water occupies three main fluid compartments 1. Intracellular fluid (ICF)  Fluid inside cells  Accounts for two-thirds of body fluid 2. Extracellular fluid (ECF)  Fluids outside cells; includes blood plasma, interstitial fluid (IF), lymph, and transcellular fluid 3. Plasma (blood) is ECF, but accounts for 3L of total body water.  Links external and internal environments (Figure 15.9) © 2018 Pearson Education, Inc. Figure 15.8 The major fluid compartments of the body. Total body water Volume  40 L 60% body weight Plasma Volume  3 L, 20% of ECF Interstitial Intracellular fluid (ICF) fluid (IF) Volume  25 L Volume  12 L 40% body weight 80% of ECF Extracellular fluid (ECF) Volume  15 L 20% body weight © 2018 Pearson Education, Inc. Figure 15.9 The continuous mixing of body fluids. Lungs Gastrointestinal Kidneys tract Blood O2 CO2 Nutrients H2O, H2O, Nitrogenous plasma Ions Ions wastes Interstitial O2 CO2 Nutrients H2O Ions Nitrogenous fluid wastes Intracellular fluid in tissue cells © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  The link between water and electrolytes  Electrolytes are charged particles (ions) that conduct electrical current in an aqueous solution  Sodium, potassium, and calcium ions are electrolytes © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Regulation of water intake and output  Water intake must equal water output if the body is to remain properly hydrated  Sources for water intake  Ingested foods and fluids  Water produced from metabolic processes (10%)  Thirst mechanism is the driving force for water intake © 2018 Pearson Education, Inc. Figure 15.10 Water intake and output. Metabolism 100 ml Feces 4% 10% 250 ml Sweat 8% 200 ml Insensible Foods 750 ml 700 ml losses via 30% skin and 2500 ml lungs 28% Beverages 1500 ml 1500 ml Urine 60% 60% Average intake Average output per day per day © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Thirst mechanism  Osmoreceptors are sensitive cells in the hypothalamus that become more active in reaction to small changes in plasma solute concentration  When activated, the thirst center in the hypothalamus is notified  A dry mouth due to decreased saliva also promotes the thirst mechanism  Both reinforce the drive to drink © 2018 Pearson Education, Inc. Figure 15.11 The thirst mechanism for regulating water intake. Plasma solutes Saliva Osmoreceptors in hypothalamus Dry mouth Hypothalamic thirst center Sensation of thirst; person takes a drink Water moistens mouth, throat; stretches stomach, intestine KEYS Water absorbed Initial stimulus from GI tract Physiological response Result Plasma Increases, stimulates solutes Reduces, inhibits © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Sources of water output  Lungs (insensible since we cannot sense the water leaving)  Perspiration  Feces  Urine © 2018 Pearson Education, Inc.  Maintaining Water Balance of the Blood  Hormones are primarily responsible for reabsorption of water and electrolytes by the kidneys  Antidiuretic hormone (ADH) prevents excessive water loss in the urine and increases water reabsorption  ADH targets the kidney’s collecting ducts © 2018 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Maintaining Electrolyte Balance  Small changes in electrolyte concentrations cause water to move from one fluid compartment to another  A second hormone, aldosterone, helps regulate blood composition and blood volume by acting on the kidney  For each sodium ion reabsorbed, a chloride ion follows, and a potassium ion is secreted into the filtrate  Water follows salt: when sodium is reabsorbed, water follows it passively back into the blood © 2018 Pearson Education, Inc.  Electrolyte Balance  Renin-angiotensin mechanism  Most important trigger for aldosterone release  Mediated by the juxtaglomerular (JG) apparatus of the renal tubules  When cells of the JG apparatus are stimulated by low blood pressure, the enzyme renin is released into blood © 2018 Pearson Education, Inc.  Electrolyte Balance  Renin-angiotensin mechanism (continued)  Renin catalyzes reactions that produce angiotensin II  Angiotensin II causes vasoconstriction and aldosterone release  Result is increase in blood volume and blood pressure © 2018 Pearson Education, Inc. Figure 15.12 Flowchart of mechanisms regulating sodium ion and water balance to help maintain blood pressure homeostasis. Falling systemic blood pressure/volume (+) Reduced filtrate volume Inhibits baroreceptors Hypothalamic or solute content in renal in blood vessels osmoreceptors tubules (+) (+) (+) (+) Sympathetic nervous Posterior pituitary JG cells of kidneys system Releases (+) Release ADH (antidiuretic Systemic arterioles hormone) Causes (+) Renin Vasoconstriction Collecting ducts Leads to of kidneys Results in Causes Peripheral resistance Angiotensin II formed in blood H2O reabsorption (+) (+) (+) Systemic arterioles Adrenal cortex Causes Secretes Vasoconstriction Aldosterone Results in Targets Peripheral resistance Kidney tubules Causes Na+ reabsorption (and H2O absorption) Results in Blood volume KEY: (+) = stimulates Rising blood pressure Renin-angiotensin system Neural regulation (sympathetic nervous system effects) Effects of ADH release © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Blood pH must remain between 7.35 and 7.45 to maintain homeostasis  Alkalosis—pH above 7.45  Acidosis—pH below 7.35  Physiological acidosis—pH between 7.0 and 7.35 © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Kidneys play greatest role in maintaining acid- base balance  Other acid-base controlling systems  Blood buffers  Respiration © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Blood buffers  Acids are proton (H+) donors  Strong acids dissociate completely and liberate all of their H+ in water  Weak acids, such as carbonic acid, dissociate only partially  Bases are proton (H+) acceptors  Strong bases dissociate easily in water and tie up H+  Weak bases, such as bicarbonate ion and ammonia, are slower to accept H+ © 2018 Pearson Education, Inc. Figure 15.13 Dissociation of strong and weak acids in water. HCI H2CO3 – – H+ – CI CI HCO3 H2CO3 H+ H+ – H+ H2CO3 – CI – CI – HCO3 CI– CI H+ H+ H2CO3 H+ H+ H+ CI– H2CO3 (a) A strong acid (b) A weak acid such such as HCI as H2CO3 does dissociates not dissociate completely completely. into its ions. © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Molecules react to prevent dramatic changes in hydrogen ion (H+) concentrations  Bind to H+ when pH drops  Release H+ when pH rises  Three major chemical buffer systems 1. Bicarbonate buffer system 2. Phosphate buffer system 3. Protein buffer system © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  The bicarbonate buffer system  Mixture of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)  Carbonic acid is a weak acid that does not dissociate much in neutral or acid solutions  Bicarbonate ions (HCO3−) react with strong acids to change them to weak acids HCl + NaHCO3 → H2CO3 + NaCl strong acid weak base weak acid salt © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  The bicarbonate buffer system (continued)  Carbonic acid dissociates in the presence of a strong base to form a weak base and water NaOH + H2CO3 → NaHCO3 + H2O strong base weak acid weak base water © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Respiratory mechanisms  Respiratory rate can rise and fall depending on changing blood pH to retain CO2 (decreasing the blood pH) or remove CO2 (increasing the blood pH) © 2018 Pearson Education, Inc.  Maintaining Acid-Base Balance of Blood  Renal mechanisms  When blood pH rises:  Bicarbonate ions are excreted  Hydrogen ions are retained by kidney tubules  When blood pH falls:  Bicarbonate ions are reabsorbed  Hydrogen ions are secreted  Urine pH varies from 4.5 to 8.0 © 2018 Pearson Education, Inc.  Developmental Aspects of the Urinary System  The kidneys begin to develop in the first few weeks of embryonic life and are excreting urine by the third month of fetal life  Common congenital abnormalities include polycystic kidney and hypospadias  Common urinary system problems in children and young to middle-aged adults include infections caused by fecal microorganisms, microorganisms causing sexually transmitted infections, and Streptococcus © 2018 Pearson Education, Inc.  Developmental Aspects of the Urinary System  Control of the voluntary urethral sphincter does not start until age 18 months  Complete nighttime control may not occur until the child is 4 years old  Urinary tract infections (UTIs) are the only common problems before old age  Escherichia coli (E. coli), a bacterium, accounts for 80 percent of UTIs © 2018 Pearson Education, Inc.  Developmental Aspects of the Urinary System  Renal failure is an uncommon but serious problem in which the kidneys are unable to concentrate urine, and dialysis must be done to maintain chemical homeostasis of blood  With age, filtration rate decreases and tubule cells become less efficient at concentrating urine, leading to urgency, frequency, and incontinence  In men, urinary retention is another common problem © 2018 Pearson Education, Inc.  Developmental Aspects of the Urinary System  Problems associated with aging  Urgency—feeling that it is necessary to void  Frequency—frequent voiding of small amounts of urine  Nocturia—need to get up during the night to urinate  Incontinence—loss of control  Urinary retention—common in males, often the result of hypertrophy of the prostate gland © 2018 Pearson Education, Inc.